You said his hair is damaged. Damaged from what?
What is his current routine? Products, styling techniques, etc. Do you guys follow the Curly Girl routine of no sulfates or silicones in your products?
There's always the possibility that as your husband got older, his natural curls loosened to waves. Hormones play a big role. I had the opposite reaction. I had stick straight, thin and shiny hair when I was kid and after puberty it got much thicker and changed to kinky, slightly wavy hair.
Medium texture, normal porosity, normal elasticity, very weak waves.
shampoo: Redken Fresh Curls
rinse out: CJ CR, TN
jellies: UFD's CM, KCCC
gels: CJ CQ, BRHG